Yes, you can transfer investments into your Dodl account. But only if they're included in the Dodl investment range.
Transferring your investments from your other provider to Dodl means you won't have to sell them before they're transferred. Your investments can stay invested, and simply move across to your new Dodl account just as they are. This is why you might hear your investment transfer be called an 'in specie' transfer - which literally translates to 'in the actual form'. You'll request your investment transfer in the usual way, by heading to 'transfer an account' in the app.
Any investments you have which aren't in the Dodl investment range won't be possible to transfer as they are. So, if you still want to go ahead with your transfer, you'll need to transfer as cash instead. A cash transfer involves selling any investments you can't transfer (you'll do this with your other provider), then requesting a cash transfer with Dodl, via the app.
β It's important to remember that selling any investments and transferring that amount as cash will mean being out of the market for the duration of your transfer and until you invest again with Dodl. So you wouldn't benefit from any potential rise in the market in that time.