Today I found custom Command Set in Document Library Web Part.
It was displayed incorrectly - instead of title I see alias from manifest file.
I know that the web part in in preview and we can expect it to work incorrectly.
But I'm just letting you know and additionally asking if you have any specific thought on when and what to expect.
Thanks!

Can you provide the manifest.json file and your commandset TS file sample code?
OK, so here is a full picture.
Initial description was a bit incorrect: Document Library Web Part uses not alias from manifest but the Title of CustomAction from elements.xml.
It's easy to reproduce:
yo @microsoft/sharepointCustomAction declaration into elements.xml to display command set in Document Library:<CustomAction
Title="DocLibTest"
RegistrationId="101"
RegistrationType="List"
Location="ClientSideExtension.ListViewCommandSet.CommandBar"
ClientSideComponentId="30d0a9a4-f3a6-4aef-9954-89a9034d22f5"
ClientSideComponentProperties="{"sampleTextOne":"One item is selected in the list.", "sampleTextTwo":"This command is always visible."}">
</CustomAction>
DocLibTest button in Command Bar of Doc Library Web Part.Please, let me know if you need more details.
Thx @AJIXuMuK, that's a strange implementation indeed and have been routed finally to right people. Sorry for the delay on the triage.
Thanks @VesaJuvonen!
we are looking into this issue and will provide update as soon as we can. Thank you
The work to enable ListViewCommandSet in webpart is done and will be available to customer in mid-late January 2019.
Will there be ability to check if the command set is displayed in web part or in regular list?
Also will there be an API to get viewId in the web part? Currently I can get it from query string and/or pageContext. What about web part? There could be multiple web parts on the page.
This feature should be enabled for customer now. Please give it a try. Thank you
Hi @ahackettms!
Thanks for the update!
I quickly looked at the functionality and it looks like there are still issues.
For example, icon for custom command set is not displayed.
iconImageUrl in Command Set manifest is set to display an icon from Azure CDN. It works fine in Document library itself, but in the web part I'm getting
<img src="" class="ms-Image-image ms-Image-image--contain ms-Image-image--portrait is-notLoaded is-fadeIn is-error image-666">
src is not set.
When the web part is added to a small zone command part is rendered with overlap

And, as I previously mentioned, it looks like there is no way to get viewId for the web part.
@AJIXuMuK the icon issue was just fixed recently. Please allow another 1-2 weeks and try again.
For the commandbar overlap issue in small webpart, @VesaJuvonen could you file a new issue for us to track that? it most likely a generic commandbar issue which is not related to client-side extensions.
For the ViewID issue, I don't think we have API supporting that. @VesaJuvonen feel free to Chime in
Hi. Seems issue with icons steel exists. Currently I get this in both cases: if iconImageUrl has value and whet it's empty
<img src(unknown) class="ms-Image-image ms-Image-image--contain ms-Image-image--portrait is-notLoaded is-fadeIn is-error image-333">
Any suggestions?
Most helpful comment
The work to enable ListViewCommandSet in webpart is done and will be available to customer in mid-late January 2019.