How Do I Change the Preference In Mac Mail To Allow “View In Place?”

A few months ago while running High Sierra, I changed my Mac Mail preferences using a Terminal command so that mail would always show attachments as “Icons.” Through the termninal command — defaults write com.apple.mail DisableInlineAttachmentViewing -bool yes — the “View in Place” option was eliminated. Today I went back to change the terminal command back to allow “View in Place” and for some reason the command — defaults write com.apple.mail DisableInlineAttachmentViewing -bool no — will not work.
Does this have somehting to do with the upgrade to Mojave? And, would anyone please be able to help me change this Mail feature back?
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JimEmmons