Hello,
You can create manual incremented sequence by using a microflow. To do so you need the following activities:
1- retrieve objects of the entity you want to increment
2- count these objects
3- create your object with sequence set to formatDecimal($count +1, ‘00000’)
Hope this helps.
Have a look at using an attribute of type AutoNumber. This will give you an increasing number for each entity created that has an AutoNumber attribute.
https://docs.mendix.com/refguide/attributes/#221-type
You can then use the StringPadLeft action in the Community Commons module in the Marketplace to help provide leading zeros if necessary.
https://docs.mendix.com/appstore/modules/community-commons-function-library/#39-stringutils
I hope this helps.