How to make it so that new entries cannot be created

[SanyaCLAUS]

 I have 2 table (and "ref" field - on photo), How can I make it impossible to create new fields in "ref" type field?

[dbaum]

In the column's Valid If property, enter an expression whose result is a list of the values you want to be available. See Drop-down on a Ref column - AppSheet Help 

[SanyaCLAUS]

And what is the condition for the "New" field?

[dbaum]

I don't understand what specifically you're asking. Maybe post a screenshot of your column's properties.

[SanyaCLAUS]

I showed you in the screenshot, I want to block the ability to add new rows by the ref field. 

In simple words, I want to make... smth like...  the field "enum" from the field "ref"

[dbaum · Accepted solution]

One approach is to change the column to Type Enum with Base type Ref. Compare the following.

[SanyaCLAUS]

Yes, that's exactly what I needed, thank you so much, good luck and have a nice day

[Joseph_Seddik]

I believe it would be necessary either for the referenced table to disallow adds, or to reference a read-only slice.