Problem with backslash

Good afternoon, dear forum users. I have a website on GetSimple CMS and trying to transfer it to GRAV CMS. But i confront into a problem: on the old site at the end of URL stand a backslash

I’m trying to make this same in GRAV in the «appended URL extension» field, but nothing changes. If I type some letters, the link changes.

But with a backslash, no.

Help me please add it