I have added a couple of new columns to my SharePoint list. They show when I initially add them but when I return to the list later they are not displayed. They are there as I can see them in the List Settings view but not in the List View. Is there a limit to the number of columns displayed?
There is no such limit of showing number of columns in list view.
If newly added columns are not showing in your list view then you need to add those columns by changing the list view settings.
You can modify the view and select as much as columns you want show in list view.
Refer below article to read about list views in sharepoint:
These columns are not enabled for that specific view. Please modify view and check whether desired columns are "checked in" (List settings -> Views -> [desired View] -> Columns). The fact that columns are showing in list settings does not mean, that they are selected to be displayed in the current view.