Appears to be a regression.

Reproduce:

Set editor to use Vim Dark color scheme.
Open source file and add side-by-side split.
Begin editing a second file in the rightmost split.
The cursor will disappear during editing (correct) but will not reappear when the mouse is moved (incorrect). You must must move the cursor outside of the split for it to be visible again and even then it will disappear again when you move it back.

Workaround:

Temporarily switch to another app and then back to Creator.