Change Activity Theme for Activities on TopoActive Maps

Is it somehow possible to change the Activity Theme during Activities on TopoActive Maps on the Fenix 8?

If you only look at the map, you can choose a theme, e.g. for mountain biking or running etc.

However, these themes are linked to an activity, so if I start the MTB activity, for example, it automatically switches to the MTB theme.
However, I don't think the theme is particularly great, on the contrary. The wide orange lines and green areas of the running theme are much easier to read.
Is there any way to change the MTB theme to the running theme?