Greetings Janet,
If you have a web map that you are bringing into Collector for ArcGIS, you should be able to make just one layer editable while the others are not.
With this in mind, the table is now included in the edit settings you choose for this layer. Here are your options for setting edit settings:
So you can choose attributes only or update features. Based on my testing, it looks like "Update features" allows attributes that are associated with point, polygon or line features to be edited but not the related records of the table.
You can also just select what layers are editable at the web map level. This video shows what that looks like:
Also keep in mind there is now Collector for ArcGIS (Classic) and Collector for ArcGIS. So when searching the documentation, be mindful of which of these are reading up on.
This is the documentation I have found that is helpful in navigating related tables and editable layers.
Collector for ArcGIS Restrict Editing
https://doc.arcgis.com/en/collector/ipad/help/prepare-layer.htm#ESRI_SECTION1_01AC3E62BCDF4E40871FCE...
Set up Related Tables in Collector
https://support.esri.com/en/technical-article/000015422
Whats New in Collector for ArcGIS
https://support.esri.com/en/technical-article/000015422
Whats New in Collector for ArcGIS (Classic)
https://doc.arcgis.com/en/collector-classic/overview/what-s-new.htm
#editing #collector