Hello,
I've released Collapsed Topics for Moodle 3.5 and 3.4 as follows:
V3.4.0.3: https://moodle.org/plugins/pluginversion.php?id=17256
V3.5.0.1: https://moodle.org/plugins/pluginversion.php?id=17257
both versions put the 'numsections' setting back.
Gareth