I was able to reproduce this issue and a bug report has been logged. Thank you for posting such clear and easy to follow steps it is greatly appreciated! You can find the report here
Keeps happening to me on 4.18.1 (the latest right now), but there’s a step missing:
2.5.Open the Editor Preferences and go to General - Loading & Saving - Startup segment and check the “Restore Open Asset Tabs on Restart” checkbox.
I have to drag out each window next to the level tab, every, single, ■■■■, time. Most times I rather just close the floating window that contains them and start all over, which then makes the “Restore Open Asset Tabs on Restart” checkbox absolutely useless.
It doesn’t look like a bug to me. In the Editor Preferences under Appearance you have “Asset Editor Open Location” set to Default. change this to Main Window and tadaaaaaa