How to "Wait for field to be not empty" in SPD 2013?

Are there too many possible values of the field? SO , we use equal to and check for all possible values and put OR between all those conditions. I understand its not very practical, if possible values are endless.

Another option is (must say this option could be too much engineering for simple requirement, however if you have to do then you have to do)

Assuming its sharepoint online (since you said workflows are retiring). Create a column on which we will check for "wait for field to be equal to".

This new field will be auto populated through automated code whenever there is change in list item. Code will actually check if your field is not equal to , if condition is true then update newly created column.

About automated code, there are three options to write this automated code.

1. Webhook
2. Timer function (this will not be synchronous though, so it depends on your requirement)
3. Remote Event receiver.

All these 3 options will involve azure setup/ dedicated server. So chose accordingly.

Being all this said, there could be better option to solve this. However, thats what i could think of as of now.