Hello again,
as you can see from the attached screenshot when you wish to open a specific deck you find all decks in a single list. Adding the feature to create folders and subfolders when saving a deck (for example folders named with formats and / or colors) and find those folders when opening a deck will make easier to search for a specific deck.
An alternative could be to create filters by format and colors for the saved decks list, also including filters for MTG Arena- only formats (Alchemy, Explorer, Historic and Timeless).
Probably the first option is more viable to implement in MTG Companion.

Hello again,
as you can see from the attached screenshot when you wish to open a specific deck you find all decks in a single list. Adding the feature to create folders and subfolders when saving a deck (for example folders named with formats and / or colors) and find those folders when opening a deck will make easier to search for a specific deck.
An alternative could be to create filters by format and colors for the saved decks list, also including filters for MTG Arena- only formats (Alchemy, Explorer, Historic and Timeless).
Probably the first option is more viable to implement in MTG Companion.