Strange happening but not sure why me?

I’m trying to a Container Stack (Source) to a Custom (Basic) but when I click that option nothing shows where I can adjust the Max Width. I have included what I’m seeing and what it is supposed to look like. Has anybody else found this problem and if so, how did you correct the problem please?

and

its rather annoying and I can’t seem to work it out. Sure there has to be a simple answer.

Thanking you,
Sabina

Sometimes you need to click away from the stack and then reselect it for a control like this to show.

I don’t know why that happens sometimes - it’s not something that is easily replicated.

Thank you. That one worked as you said. I had saved a project last night and then when I opened it today, the background image had disappeared and nothing I did would it let me re-input it. Finally, today I rebooted mac and it was there. Hm…
Sabina