What to do if I don't want to block certain website(-s)?

Use AdGuard Assistant. It is a tool that helps you manage filtering right from Safari without switching back to the app. Open Safari, tap on the arrow-in-a-box symbol, scroll down to AdGuard/AdGuard Pro (depending on the app you use) and tap it to fetch a window with several options.

Turn off "Enable on this page". Go to Allowlist (Settings → Safari protection → Allowlist) and add there the domain name of the website that you don't want to be blocked (for example, enter "example.com" and not "example.com/page/address.html").

Note that you don't have to remove the website from Allowlist to resume filtering there, just tap the ✔️ mark to disable/enable Allowlist for it at any time.