Would you be willing to provide more detail around your use case for such a long dropdown list? While it might be technically possible to make a list that long, there might be a more efficient and easier-to-maintain solution to your use case.
At the very least, reacting to the fact that you made this post in the Admin space, we might be able to discuss a method for creating the solution without needing to manually make the list in Admin > DropDown Editor.
The use case is I need to create a dropdown list for car agencies, about 600, and I need to crate a dropdown list for sales team andf relate it with car agencies dropdown, my client think is more efficient this way to relate their information, I prefer create two new modules for each one.
My client no response yet, but, if they don't want use modules I need to know if is possible insert 600 elements into a dropdown list.
In theory there is no limit for dropdown size, but users may face performance degradation on rendering huge dropdown lists.
The best approach is to setup 2 modules, create those relationships to base module and then customize the related field definition in the viewdefs (record) in order to filter the child relate field according to selection on the parent one.
In a maintenance perspective it is better to manage modules instead. You can easily import data in order to update existing records or adding new ones.
