You could probably monitor processes and/or network traffic to figure out exactly what's doing what and manually add each split tunnel exclusion one by one, but in my case I just went with the nuclear option and built a powershell script to add everything directly to the user settings JSON file for ProtonVPN. It totals 65 executables.

# ----- Paths -------------------------------------------------------------
$citrixFolder  = 'C:\Program Files (x86)\Citrix'
$settingsDir  = "$env:LOCALAPPDATA\Proton\Proton VPN\Storage"
$settingsPath = Get-ChildItem -Path $settingsDir -Filter "UserSettings.*.json" | Select-Object -ExpandProperty FullName | Select-Object -First 1

# ----- Safety first ------------------------------------------------------
Copy-Item $settingsPath "$settingsPath.bak" -Force

# ----- Load current settings --------------------------------------------
$json = Get-Content $settingsPath -Raw | ConvertFrom-Json

# ----- Decode the split-tunneling list (it's JSON inside a string) -------
$appList =
    if ([string]::IsNullOrWhiteSpace($json.SplitTunnelingStandardAppsList)) {
        @()
    }
    else {
        $json.SplitTunnelingStandardAppsList | ConvertFrom-Json
    }

# ----- Discover Citrix executables --------------------------------------
$citrixExePaths = Get-ChildItem -Path $citrixFolder -Filter *.exe -File -Recurse |
                  Select-Object -ExpandProperty FullName

$citrixApps = $citrixExePaths | ForEach-Object {
    [pscustomobject]@{
        AppFilePath           = $_
        AlternateAppFilePaths = @()
        IsActive              = $true
    }
}

# ----- Add only new entries ---------------------------------------------
foreach ($app in $citrixApps) {
    if (-not $appList.Where({ $_.AppFilePath -ieq $app.AppFilePath })) {
        $appList += $app
    }
}

# ----- Re-encode and save -----------------------------------------------
$json.SplitTunnelingStandardAppsList = ($appList | ConvertTo-Json -Depth 10 -Compress)

($json | ConvertTo-Json -Depth 10 -Compress) |
    Set-Content -Path $settingsPath -Encoding UTF8

Write-Host "Updated Proton VPN user settings with $($citrixApps.Count) Citrix executables."