v2.0.2
KDE Frameworks 5.26.0
Qt 5.6.1 (built against 5.6.1)
The xcb windowing system

I just had to check to see if Marble is under current development (answer: yes, apparently) because it has over time accumulated a number of bugs that are never dealt with. Examples:

https://bugs.kde.org/show_bug.cgi?id=371010 "Position Marker is gone/invisible" has been unconfirmed for six months. In it, I also reported invisible tracks (actually thin white lines on a light-colored background) because it occured at the same time, coincident with the 16.08 release. That should possibly be in a separate report.

The above bug obscures https://bugs.kde.org/show_bug.cgi?id=324872 "Position Marker configurator won't save colors", unconfirmed for three years, in which any change is not applied to the next Marble restart. In fact, the default configuration is not applied to a Marble restart, which instead uses an opaque black circle to show accuracy estimates.

I have not reported that Marble does not apply its previous position/desktop on the next KDE restart, possibly coincident with the switch to KF5, or that it starts with a default track that must have been saved somewhere/sometime.

Is it worthwhile reporting these bugs?

Yes, please report those bugs.

Position tracking on the Desktop is a less often used feature, so issues can go unnoticed for some time. Patches are highly welcome of course. The issue with thin white track lines for example is likely related to the introduction of StyleBuilder, in particular one commit that moved default styles to it. A fix needs to connect track styles with StyleBuilder to derive the default style from it and assign it.