Macro: System displays chain as two sequences

[AlexeyGirin]

Steps to Reproduce

1. Switch to Macro
2. Load from file: System displays nucleotide as @ symbol.zip
3. Switch to Sequence mode
   

Actual behavior
System displays chain as two sequences

Expected behavior
System shows one sequence

As per specification:

In sequence view nucleotide should be displayed as a letter which corresponds to the natural analog of base that is a part of nucleotide. If nucleotide has a modified component (phosphate, sugar, or base), then a letter should be marked by some unambiguous designation (see mockups in comments).

Modified phosphate - any phosphate except 'P'
Modified sugar - any sugar except 'R'
Modified base - any base except 'A', 'C', 'G', 'T', 'U'

Versions:
Windows 10
Chrome Version 112.0.5615.138 (Official Build) (64-bit)
Ketcher Version 2.20.0-rc.2 Build at 2024-04-02; 05:31:05
Indigo Toolkit Version 1.20.0-dev.1.19-gd0224f91-wasm32-wasm-clang-12.0.0

Issue found in the context of testing - #3734

[Zhirnoff]

The issue has been moved from 2.21.0-rc.2 to 2.22.0-rc.1 after discussion with management and in accordance with the testing flow process.

[AlexeyGirin]

Moved to Refined Backlog since not fixed over 1 release