it seems that functional indexes are listed twice if there are two functions within the index columns.....
Example (Content from the indexes tab of the table view):
owner ....._PK UNIQUE VALID NORMAL N NO NO ....._UUID
owner ....._UI1 UNIQUE VALID FUNCTION-BASED NORMAL N NO ENABLED NO SYS_NC00016$, SYS_NC00017$, ....._ID, ....._PLAN_ID SYS_EXTRACT_UTC("....._START")
owner ....._UI1 UNIQUE VALID FUNCTION-BASED NORMAL N NO ENABLED NO SYS_NC00016$, SYS_NC00017$, ....._ID, ....._PLAN_ID SYS_EXTRACT_UTC("....._END")
Both functions are in the same index "....._UI1".
The detail panel shows the same details.
What version of SQL*Developer?
I am using 3.2.20.09 and created 2 function-based indexes on a practice employee table, upper() on both first and last names. When displaying indexes through the table display using the Indexes tab and through the object navigator using indexes I only see each index once.
On a second pass I created a third composite index with upper on both first and last names and got the results similar to those you describe in both places. The column names (expression name in the table index pane) were different.
Version 126.96.36.199, Build MAIN-12.27