Can't zoom out. Want to locate custom zoom.

Scroll should work up/down. To be honest I don’t know the actual pixel level. And it will depend if you have an original or smart preview available. Using the scroll-wheel could be like zooming (stretching) in a browser window. But I find it helpful sometimes e.g. when examining the green or purple fringing to correct chromatic aberration along high contrast edges.

The presets above 1:1 are only available in Lightroom Classic. The new cloud version has a maximum of 1:1 but depending on your set-up there may be a work around. For example when I work in the Edit module and zoom to 1:1 I can hold down the ctrl key and zoom greater than 1:1 by using my mouse scroll wheel. Let us know if that works for you.

It will help us to answer your question if you could provide the exact version number you have installed and details of your operating system e.g.
• Windows 10 v1809, MacOS Mojave (10.14) Catalina (10.15)
• Adobe Photoshop Version: 20.0.6 20190724.r.80 2019/07/24
You can find this from your application menu:
Help >> System Info