This occurs for me as well. I’ve been meaning to make a post about it for a while, but it has kept slipping my mind. I believe this started once I updated to Mojave too. I can post specs and a recording once I get home later.
Edit: I forgot about this yesterday, sorry about that. Anyways, here’s the video I’ve got of it occurring. Whenever I have to open finder through Studio, not just through “Open from File” option, it always is really laggy; I have never had any lag while using Finder outside of Studio so it’s not that my mac is slow.
I was having trouble uploading it here, so I’ve put it on YouTube instead. It may be hard to see, but the majority of my clicks are delayed by 2 - 3 seconds during which my entire OS is frozen. When I have it open the second time, I start scrolling the sidebar immediately and is once again delayed.
Just to add a little more information, this happens to me when I try to upload a file to Roblox via the create/develop page. I choose to simply have a finder window open, and drag the file onto the button, as it’s much faster.
There’s the possibility that this issue is an OS issue, not a Roblox issue.
I’ve had the same problems as well. When I open studio from a file, or open studio from the app, my MacBook freezes. This does not happen when I click on “Edit” in the develop page or from the game page. This also happened when Mojave first came out, I wasn’t even able to open Studio, or a Roblox game at all.
However I do see you are running,
I am currently running on Mojave 10.14.5, and that problem seems to be fixed. Maybe updating your OS may help.