If they haven't already been tried, the following might help.
1. From the timing of when the program became problematic, the notes in
my post here could well be relevant.
2. Right-clicking on the taskbar in the Windows 10 allows one to select the Task Manager. I would do this before running The HTML Editor to note the percentage shown in the Processes tab of usage of the CPU, Memory, Disk, and Network. With the Task Manager still running I would then start up The HTML Editor and see what changes there are to the noted usage of the above items
(a) immediately,
(b) after closing the Tips and Welcome boxes, and
(c) when clicking on items that caused the perpetual hourglass and message at the top.
This may reveal whether hardware resources are being overstretched, possibly because some other program/process (perhaps malware or some newly added program) is hogging them.
Frank