The "Save File"-dialog in Kap, appearing when clicking on "Export" a recording, is broken under macOS 10.14 Mojave (Beta 2 release). It also doesn't support the Mojave Dark Mode.
I cannot access a screenshot of the problem at the moment, but will add this later to the issue here.
Would be interesting to know, if this is an implementation issue with that feature in Kap - or coming from the OS? However, so far all other apps "Save File"-dialogues in Mojave have not shown this broken behaviour…
macOS Version: macOS 10.14 Beta 2 (18A314h) Mojave
Kap Version: Version 2.2.0 (2.2.0.880)
Can reproduce/confirm. Let me know if you need more information.
I have to add: it's still possible to save/export a recording - so no big deal. But it looks strange...
Here's a recording of the issue:

Whoa, there's quite a bit going awry in that recording @oliveratgithub! Frankly, supporting 2.0 on Mojave isn't being prioritised. Instead we're optimising the next version of Kap for Mojave, and will aim to support it on macOS 10.12 or later.
Could you test to see if you're able to recreate this using master on the latest macOS Mojave @oliveratgithub and @dodekeract?
Related issue #368, this is also likely upstream.
Duplicate of #368
Dark mode for the save dialog will be fixed by https://github.com/wulkano/kap/pull/567.
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I have to add: it's still possible to save/export a recording - so no big deal. But it looks strange...
Here's a recording of the issue:
