Not AFAIK. For a previous version, a widget that was able to lock the play bar existed, but not for recent versions.
Is the progress indicated in the TOC not an alternative? I almost never use the default play bars, because they can also be confusing for a non-linear course (branching) or for courses where slides are not necessary visited by everyone.
You can also insert a text container - on master slide or displayed for rest of project - that mentions which slide out of the total number of slides they are at that moment.
Lilybiri