The latest update should make a real difference here, and we'd like your help checking it.
Muse 1.0.38 brings a set of efficiency and reliability improvements aimed at libraries your size. Switching collections, opening All and searching are all quicker, the Timeline is built to handle thousands of items landing on the same day, and background work such as tagging now waits until you pause so it never competes with what you are doing.
Muse should automatically ask you if you'd like to update, and if not, you can open Settings and check for updates. Once you are on 1.0.38, please give the Timeline and the rest of the app a go with your Eagle library and let us know how it feels, and anything that still seems slow or out of place. We'll work through it with you from there.
Any other issues or feedback, please just get back in touch and let us know.