As far as I can tell, Cosmos DB no longer supports creating collections via Studio 3T. I am always presented with the error "Shared throughput collection should have a partition key" when following the instructions listed above.
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@ericbarch Thanks for your feedback! We will investigate and update soon on it.
@ericbarch I have followed the same document and able to create databases, collections, and documents with Studio 3T tool.

Could you share the steps which you have followed, and which step does it throws this error message “Shared throughput collection should have a partition key”?
@ericbarch We will now proceed to close this thread. If there are further questions regarding this matter, please comment and we will gladly continue the discussion.
I get this error when I follow this exactly from Studio3T:
SERVER [URL.documents.azure.com:10255] (Type: UNKNOWN)
|_/ Connection error (MongoSocketOpenException): Exception opening socket
|____/ I/O error: connect timed out
Details:
Timed out after 30000 ms while waiting to connect. Client view of cluster state is {type=UNKNOWN, servers=[{address=splc-ip-mongo-1.documents.azure.com:10255, type=UNKNOWN, state=CONNECTING, exception={com.mongodb.MongoSocketOpenException: Exception opening socket}, caused by {java.net.SocketTimeoutException: connect timed out}}]
I have this same issue with Robo3t and Mongoose.
Here is a screenshot from Robo:

Also from Mongoose:
(node:75409) UnhandledPromiseRejectionWarning: MongoError: Shared throughput collection should have a partition key
console.pub.js:42
ActivityId: 7b53602c-0000-0000-0000-000000000000, Microsoft.Azure.Documents.Common/2.2.0.0
at Function.MongoError.create (/Users/chriskarkowsky/Documents/workspace/us-express/node_modules/mongodb-core/lib/error.js:31:11)
at /Users/chriskarkowsky/Documents/workspace/us-express/node_modules/mongodb-core/lib/connection/pool.js:497:72
at authenticateStragglers (/Users/chriskarkowsky/Documents/workspace/us-express/node_modules/mongodb-core/lib/connection/pool.js:443:16)
at Connection.messageHandler (/Users/chriskarkowsky/Documents/workspace/us-express/node_modules/mongodb-core/lib/connection/pool.js:477:5)
at TLSSocket.<anonymous> (/Users/chriskarkowsky/Documents/workspace/us-express/node_modules/mongodb-core/lib/connection/connection.js:331:22)
at TLSSocket.emit (events.js:189:13)
at addChunk (_stream_readable.js:284:12)
at readableAddChunk (_stream_readable.js:265:11)
at TLSSocket.Readable.push (_stream_readable.js:220:10)
at TLSWrap.onStreamRead [as onread] (internal/stream_base_commons.js:94:17)
(node:75409) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
This is not an issue with document-set throughput, instead of shared across the database.
The ONLY exception is for a fixed collection where a partition key is not required. As soon as you introduce partitioned containers, you must use a partition key.
I manage to connect to CosmosDB using Studio3T, but Studio3T does not see any collection, although I created them in the CosmosDB mamagement interface.
It is not clear for me either how to perform a "clear" of a collection using CosmosDB (meaning deleting all the documents without droping the collection).
I trying using Python, but CosmosDB doesn't accept Collection.delete_many({})
Same with me I'm able to connect but does not able to see any collections using Studio 3T, It shows collections in Robo 3T
I have the same problem as @gnumarco and @BKB503.
@ziziz @BKB503 @gnumarco If you are creating a fixed partition where a partition key is not required, you will likely have a more useful experience with any 3rd Party client. In the case where a partition key is required, you will experience issues. Can one of you create an entry in the Cosmos DB User Voice while the others upvote and comment on the one entry that was created? This will be super helpful in communicating to the product group that 3rd Party client tools are desired. Thank you!
Additionally, Cosmos DB is moving towards requiring a partition key in all cases. I see this is an older issue and not requiring a partition key was available for a fixed collection.
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I manage to connect to CosmosDB using Studio3T, but Studio3T does not see any collection, although I created them in the CosmosDB mamagement interface.
It is not clear for me either how to perform a "clear" of a collection using CosmosDB (meaning deleting all the documents without droping the collection).
I trying using Python, but CosmosDB doesn't accept Collection.delete_many({})