Moving flatpak to separate partition

Preparations

sudo mkdir -p /etc/flatpak/installations.d/
cat > /etc/flatpak/installations.d/extra.conf <<-EOF
[Installation "myFlatpaks"]
Path=/path/to/location/
DisplayName=myFlatpaks Installation
StorageType=harddisk
EOF

Reinstallation

flatpak remote-add flathub https://flathub.org/repo/flathub.flatpakrepo --installation=myFlatpaks
flatpak remove  com.discordapp.Discord --system
flatpak install com.discordapp.Discord --installation=myFlatpaks

Although installation with --user should be simplier