Hi @by1,
do I get it right that you want to add The Graph (GRT) as ERC20 token on the Ethereum network? If so, please find the information on how to use ERC20 tokens in Trezor Suite in the video linked at How to use ERC20 tokens in Trezor Suite
Stellar (XLM) on the other hand has its own mainnet. This cryptocurrency is supported in Trezor devices, however, it is not natively supported in Trezor Suite. It means that you need to use 3rd party application that supports Trezor devices and also desired cryptocurrency. For Stellar you can use for example Account Viewer.