It seems that Papyrus' preference settings for Class Diagrams Operations only contains a subset of label attributes from those found under an operation's Appearance tab. Most notably are the absence for options to enable/disable Parameter Name and Return Type labels. A cursory review of other preference panels didn't come up with a solution either.
I am relatively new to Papyrus. Hopefully this is just a case of me not seeing the forest for the trees and that with time its various nuances and secrets will become more evident.
Unfortunately, I became quite unsettled when my Return Types weren't displayed anymore after twiddling with the preferences. The only recourse that seemed obvious at that time was to manual enable labels for each operation, which I didn't look forward to. Instead a little digging on my part uncovered where these preference are stored in hopes of setting global options once, even if not fully accessible via preferences.
Operation label display settings are stored in the following preference file
under the key
Note: this key may be not be defined if you have never tweaked your preference settings. The key is a 32-bit integer whose bit position definitions are as follows:
Bit Label Display Options Numeric
--- ------------------------ -------
0 n/a 1
1 Visibility 2
2 n/a 4
3 Name 8
4 n/a 16
5 n/a 32
6 n/a 64
7 Modifiers 128
8 Parameter Type 256
9 Return Type 512
10 n/a 1024
11 Parameter Direction 2048
12 Parameter Name 4096
13 n/a 8192
14 Parameter Multiplicity 16384
15 Parameter Default Value 32768
16 Parameter Modifiers 65536
For example, to globally enable operation display labels for Visibility (2) + Return Type (512) + Parameter Type (256) the options value would be 770 = 2 + 256 + 512. Adding/replacing
in the above mentioned preference file will set those global attributes accordingly. While this is not an elegant solution, it certainly is far more flexible than setting all my operation label options manually.
Hopefully, someone will point out an easier method for accomplishing the same.