Tabr is a free manager for Chrome tabs.

Tap the Tabr icon and it displays very large thumbnails of any open tabs, making it easier to find what you need.

Hovering your mouse cursor over a tab reveals options to move it to a new window, close it, or "archive" it (save the tab status before you close it, so you can quickly restore it later).

An "Archive Session" option saves the state of every open tab as a group. You could then close one or more tabs to free up RAM, and restore the entire session at a later date to carry on where you left off.

An "Auto-Archive" feature automatically archives tabs after they've been idle for a set number of minutes. We're unsure whether that's more likely to save RAM, or just be very annoying, but it's easily disabled if the option doesn't work for you.