Click with secondary (right) mouse button on any file tab to open the context menu. Open from context menu the submenu File tabs and click on menu item Show tooltips to toggle this option on.

Fleggy, I see a different behavior as you have described with UES v17.10.0.15 and UE v24.10.0.24.

When there are two files reloaded on startup of UltraEdit and second file is the active file and I move the mouse pointer over the file tab of second file, I get displayed the tooltip with full file path, file size, creation and last modification date. But moving the mouse pointer over the first file tab of not active file, the tooltip is not shown. I have to make the first file active to get displayed the tooltip on moving mouse pointer over it. The tooltip is then always shown for both files on moving the mouse pointer over the file tabs independent if the file is the active file.

But this issue occurs only non dockable file tabs are used (as by default) document window of active second file after reload covers the document window of non active first file completely. If the document windows of the files are arranged side by side vertically or horizontally or dockable file tabs are used, the tooltip is displayed after startup for both file tabs.

It looks like the startup optimization is responsible for this different behavior on displaying tooltip for non active file after startup and automatic reload. When non dockable file tabs are used and the document window of a non active file is covered completely by another document window, the file contents of this file are not loaded at all on startup and for this reason the file tab tooltip object for such a file is not created at all or is not initialized at all with the appropriate data for the file.

So this is a very minor issue as all to do to get displayed the tooltip for a file not being active after reload on using non dockable file tabs and of which document window is completely in background is making this file active and then move the mouse pointer a little bit over file tab to get the tooltip displayed.