The biggest single challenge faced, so far, is traversing the tabbed menu level list to identify relevant levels (e.g. when selecting a particular template level to copy from/to).

That can be solved by giving the levels/tabs names that makes sense for the level. One method I use is "0[250]" where 0 is the level elevation and 250 is the height. That is particularly useful when you have multiple levels with different heights. Sometimes I split the furniture from the actual plan and add a level at the same elevation naming it "0[250]F". For me that's an easy way to identify the level and it's furniture level. For template levels you could use something like "Walls1", "Walls2", "Foundation1", "Damp1". Optionally extended with the elevation/height numbers.
Try to keep the tab names as short as possible to avoid too many rows of tabs.

If you work with templates for copying to other levels you can also think about having a second project with only the templates. Make one template level the only visible one, Ctrl-A, Ctrl-C, and paste in the production project. This limits the number of levels/tabs in each project and makes traversing easier.