I updated some system variable in Homematic CCU (added some new, but also removed some unused).
To get the variable updated in OH3, its required to remove the Gateway thing and add it again (at least this is the only process I’m aware)
The Channels listed for the Gateway things are updated correctly in the UI.
However, I found some system log, referring to some of the remove system variables.
2023-07-30 10:21:00.309 [WARN ] [ternal.handler.HomematicThingHandler] - Datapoint 'GWE00000000:1#b_sonnenschutz_Sued' not found on gateway 'xxxxxxxxxx'
2023-07-30 10:21:00.311 [WARN ] [ternal.handler.HomematicThingHandler] - Datapoint 'GWE00000000:1#b_sonnenschutz_ost' not found on gateway 'xxxxxxxxxx'
Those are not available in the UI anymore, but still in the file thing.json file.
Seems this isn’t updated properly, when the Gateway thing was removed/added.
[Stefan@WeWeNAS-3 jsondb]$ grep b_sonn *
org.openhab.core.thing.Thing.json: "uid": "homematic:GATEWAY-EXTRAS-xxxxxxxxxx: xxxxxxxxxx:GWE00000000:1#b_sonnenschutz_ost",
org.openhab.core.thing.Thing.json: "id": "1#b_sonnenschutz_ost",
org.openhab.core.thing.Thing.json: "channelTypeUID": "homematic:GATEWAY-EXTRAS-xxxxxxxxxx_1_b_sonnenschutz_ost",
org.openhab.core.thing.Thing.json: "uid": "homematic:GATEWAY-EXTRAS-xxxxxxxxxx: xxxxxxxxxx:GWE00000000:1#b_sonnenschutz_Sued",
org.openhab.core.thing.Thing.json: "id": "1#b_sonnenschutz_Sued",
org.openhab.core.thing.Thing.json: "channelTypeUID": "homematic:GATEWAY-EXTRAS-xxxxxxxxxx_1_b_sonnenschutz_Sued",
[Stefan@WeWeNAS-3 jsondb]$
Hopefully @MHerbst can help with this issue?
Many thanks 
Stefan