In some case I.E. some Espressive devices or the Nuki smart lock 3.0pro, the DTIM interval can improve stability and performence for connection.

Unfortunately, the default one is not the best for these kind of devices.
Having the ability to modify it could help improve user experience and allow avoiding disconnection issues.

Could it be possible to add a setting to modify the Delivery Traffic Indication Message interval in the Deco app?

Sources:
ESPHome FAQ about frequent disconnection issues.

Also the Post 27 in the topic about firmware 3.7.x beta in the Nuki developer forum, because I cannot post any link I can only summarise where I find this information.