The method initializes a new substitution.

After specifying substitution details you need to save the substitution by calling the ReplacementItem.save mehtod.

// Let's create  a substitution for an employee who is going on holiday 
const rpl = System. replacements.create(); 
rpl.data.type = rpl.fields.type.variants.reassign;  
rpl.data.absent = Context.data.__createdBy; 
rpl.data.replacement = Context. data.substitution; 
rpl.data.begin = Context.data.vacation_start;  
rpl.data.end = Context.data.vacation_end; 
await rpl.save(); 

The method searches for substitutions.

To search for items in the collection, use the Search object:

const replacements = await System.replacements.search()
    . where(r => r.absent.eq(Context.data.absent_user)) 
    .all(); 

Read more about using search in the article about the user search object.