Maybe this is a bug, maybe it's just an incredibly badly thought out feature. I created a layout with this search, and saved the layout. Note I am searching the NRSV interlinear, and my secondary search text is the Lexham English Septuagint.

I then created a different layout, with this search, and saved the search. Note I am searching the Qumran Biblical Dead Sea Scrolls Databse, and my secondary search text is the Dead Sea Scrolls Study Edition (Translations).

Then I re-opened the original layout, only to discover the search had been changed; note the secondary search text is now the Dead Sea Scrolls Study Edition (Translations), instead of the Lexham English Septuagint, which is what I had set it to.

So I changed the secondary search text back to the Lexham English Septuagint, and re-saved the layout. I then returned to my Qumran texts layout, only to find that this had now been changed; the secondary search text is now the Lexham English Septuagint, not the Dead Sea Scrolls Study Edition (Translations), which I had set it to.

The same thing happens when you create multiple search tabs in a single layout; the secondary text always changes to the secondary text you used in your last search. It's particularly unsatisfying when you spend a lot of time carefully setting up four different layouts, only to find that Logos will arbitrarily change them even while they're closed, and you need to keep resetting them back the way you want them. It defeats the purpose of designing and saving layouts in the first place.