What's a word that's in between "experiment" and "play"?

Probe, venture, explore, speculate.

Noodle

Toy as in toy with.

tinker?

adventure

I think “explore” (offered by @erichw1504) sounds closest to your intended meaning as described. You’re exploring an idea or a concept or a possibility.

Ascertain

Entertain (an idea or thought)?

Most of these are used as verbs: voyage, journey, dig, nose, dabble, wander, open, unearth, root, dance, immerse, jump in, kick around, awaken, fly through, tinker, and I also like adventure.

test

I like @anartist ‘s synonym.

How about just plain ol’ try it out?

Or the futuristic: engage in

i like all of these, especially explore. thanks guys.

Dabble.