Your system information

• Steam client version (build number or date): 2020-10-28
• Distribution (e.g. Ubuntu): Ubuntu 20.04 LTS
• Opted into Steam client beta?: [Yes/No] No
• Have you checked for system updates?: [Yes/No] Yes

Please describe your issue in as much detail as possible:

Describe what you expected should happen and what did happen. Please link any large code pastes as a Github Gist

When adding a non-steam game, Steam client does not properly register game if there is a space in the path.

Here is the .desktop file:

[Desktop Entry]
Encoding=UTF-8
Value=1.0
Type=Application
Name=Nightmares from the Deep: The Cursed Heart
GenericName=Nightmares from the Deep: The Cursed Heart
Comment=Nightmares from the Deep: The Cursed Heart
Icon=/home1/ralmond/Games/Nightmares from the Deep The Cursed Heart/support/icon.png
Exec="/home1/ralmond/Games/Nightmares from the Deep The Cursed Heart/start.sh" ""
Categories=Game;
Path=/home1/ralmond/Games/Nightmares from the Deep The Cursed Heart

When imported into Steam, I get the following in the properties dialog:

Two issues are visible, one is not.

1. The pathname is truncated at the first space.
2. There seems to be a redundant quote in front of both the application and directory name.
3. [Not in screen shot] The icon (note space in pathname) is not found.

Additionally, if I have two games whose paths are the same up to the first space (in this case "Nightmares from the Deep 2") Steam will not see the second game even if I explictly navigate to and select the .desktop file.

Steps for reproducing this issue:

1. Install a non Steam game with a space in the pathname.
2. Select "Add a Game> Add a non-steam game ..."
3. Select the .desktop file for the game.

Two example .desktop files are pasted below.
Nightmares_from_the_Deep_2_The_Sirens_Call_1.desktop.txt
Nightmares_from_the_Deep_The_Cursed_Heart_1.desktop.txt