Hi Sona,
Thanks for your post. No such option exists in Pro, because once transparency is applied to a layer's symbology in a map, this should be automatically reflected in the legend. Here is an example.
Is the map that you're updating, the same as the map frame in your Layout? There are a couple way's to check this:
In Layout view, right-click the map frame and go to Properties. On the Element pane under Options > General look to see that the Name is the map name + Map Frame:
![](/legacyfs/online/123025_pastedImage_5.png)
Or, if you right-click the map frame in Layout view and choose Activate to activate the map, go to the Contents pane and right-click your layer symbol > Color Properties, and change the transparency. Once transparency is applied, click the Layout tab > close activation. Observe the Legend-- does it reflect this change in transparency? If so, its likely that the map you were updating originally is not the same as the map in your Layout.
I hope this is helpful. If you continue to see issues with the updating of legends, let us know and we'll continue to investigate.
Thanks,
Kirsten