Open Neovide directly or use Neovide from the 'Open with' menu to open files.

neovide.applescript

on replace_chars(this_text, search_string, replacement_string)
	set AppleScript's text item delimiters to the search_string
	set the item_list to every text item of this_text
	set AppleScript's text item delimiters to the replacement_string
	set this_text to the item_list as string
	set AppleScript's text item delimiters to ""
	return this_text
end replace_chars

on activate_open_instance(win_title, is_first_time)
	tell application "System Events"
		set neovideProcList to a reference to (every process whose name is "neovide")
		repeat with proc in neovideProcList
			set PID to proc's unix id
			set myFiles to paragraphs of (do shell script "lsof -F -p" & space & PID & space & "| grep ^n/ | cut -c2-")
			set fName to my replace_chars(win_title, "'", "")
			if myFiles contains fName then
				tell proc
					set frontmost to true
				end tell
				return true
			end if
		end repeat
	end tell
	
	return false
end activate_open_instance

on run {input, parameters}
	if input is not {} then
		set posixPaths to {}
		
		repeat with fileItem in input
			set posixPath to POSIX path of (fileItem as text)
			set end of posixPaths to quoted form of posixPath
		end repeat
		
		set AppleScript's text item delimiters to space
		set filePathsString to (posixPaths as string)
		set AppleScript's text item delimiters to ""
		
		set firstPosixPath to item 1 of posixPaths
		
		if true or not my activate_open_instance(firstPosixPath, false) then
			set enablePathVar to "eval \"$(/usr/libexec/path_helper -s)\"; PATH=$PATH:/opt/homebrew/bin neovide"
			set cmd to "$(/usr/bin/env neovide)"
			
			do shell script enablePathVar & space & cmd & space & filePathsString
			delay 0.3
			my activate_open_instance(firstPosixPath, true)
		end if
	else
		set enablePathVar to "eval \"$(/usr/libexec/path_helper -s)\"; PATH=$PATH:/opt/homebrew/bin neovide"
		set cmd to "$(/usr/bin/env neovide)"
		
		do shell script enablePathVar & space & cmd
		delay 0.3
		my activate_open_instance("", true)
	end if
	return input
end run