Thanks for bringing this up - a lot of users transitioning from other platforms run into similar scenarios.
If your Mutual Fund holdings are in Demat mode, you can absolutely continue to invest and redeem mutual funds from Dhan - once they’re fully transferred to your Dhan demat account.
You can find the detailed steps for transferring demat mutual funds here:
Transfer to Dhan – Step-by-Step Guide
Since you’ve invested in ELSS schemes that are still under the 3-year lock-in period, you’ll need to use the closure-cum-transfer method to move those units from your current broker to Dhan.
Once transferred, you can continue investing in those ELSS schemes via Dhan - but do note, the original lock-in period will still apply until it completes.