[BUG]: Enrichment of model from document in Create Model from Equations misses all parameters and variables of the form X_{i}

[liunelson]

Describe the bug
A clear and concise description of what the bug is.

The source document clearly contains descriptions of several quantities with subscripts in their name, for example S_{f}, I_{f}, \lambda_{f}, ...`

The generated model description contains the descriptions of all the states but only some of the parameters - those parameters with subscripts are missing (N_{f}, \lambda_{f}, \lambda_{m}, ...)

The model metadata itself is worst: both states and parameters with subscripts are missing their description, despite being such info being partially extracted in the model description and clearly defined in the document:
However,

To Reproduce
Steps to reproduce the behaviour:

1. Use this paper: https://www.sciencedirect.com/science/article/pii/S2666818124001499
2. Use these equations:

\frac{d S_f}{d t} = - \phi S_f - \frac{1}{N_m} d_f \beta_m I_m S_f + \omega V_a
\frac{d V_a}{d t} = \phi S_f - \omega V_a - \frac{1}{N_m} d_f \beta_m I_m (1 - \varepsilon) V_a 
\frac{d I_f}{d t} = \frac{1}{N_m} d_f \beta_m I_m S_f + \frac{1}{N_m} d_f \beta_m I_m (1 - \varepsilon) V_a - \delta I_f - \mu_f I_f 
\frac{d P}{d t} = \delta I_f - \theta P - \xi P
\frac{d C}{d t} = \theta P
\frac{d R_f}{d t} = \mu_f I_f + \xi P
\frac{d S_m}{d t} =  - I_f S_m\frac{1}{N_f} d_m \beta_f  -  P S_m \frac{1}{N_f} d_m \beta_f \eta
\frac{d I_m}{d t} = I_f S_m\frac{1}{N_f} d_m \beta_f  +  P S_m \frac{1}{N_f} d_m \beta_f \eta - \mu_m I_m
\frac{d R_m}{d t} = \mu_m I_m

3. Inspect the model description and not the absence of subscripted parameters
4. Note the absence of description on all states and parameters with subscripts