Is there a format suitable for importing branched sequences? If so, what does it look like or where can I find an example of it?

Is there a format suitable for importing branched sequences? If so, what does it look like or where can I find an example of it?

ST.26 Annex VI is a guidance document which provides various example sequences, advises whether they should form part of an ST.26 sequence listing and how to provide this
information. Example 7(a)-1 has an example of a branched nucleotide sequence listing and Examples 7(b)-2 & 3 are examples of a branched amino acid sequence listing.