Angular : how to hide parameter in url?

There are a few things that you'll have to do:

1. Remove the /:userId from your editModelingAgency child route.
2. Create a service that will get and set the userId of the user to edit.
3. Inject the service both in your EditModelingAgencyComponent(to get) and in your ModelingAgencyComponent(to set)

There are also a few caveats though, the most important one would be, that you will not be able to support if the user lands directly on /base/editModelingAgency route. That being said, here's a code eg:

Your SharedService:

import { Injectable } from '@angular/core';
import { Observable, BehaviorSubject } from 'rxjs';

@Injectable()
export class SharedService {

  private userId;

  set userToEdit(userId) {
    this.userId = userId;
  }

  get userToEdit() {
    return this.userId;
  }

}

Your ModelingAgencyComponent Class:

import { Component, OnInit } from '@angular/core';
import { Router } from '@angular/router';
import { SharedService } from '../shared.service';

@Component({...})
export class ModelingAgencyComponent {

  constructor(
    private router: Router,
    private sharedService: SharedService
  ) {}

  navigateToEdit() {
    this.sharedService.userToEdit = 15;
    this.router.navigate(['/base/editModelingAgency']);
  }

}

Your ModelingAgencyComponent Template:

<ng-container matColumnDef="action">
  <th mat-header-cell *matHeaderCellDef> Action </th>
   <td mat-cell *matCellDef="let element">
     <button mat-raised-button (click)="navigateToEdit()"></button>
   </td>
 </ng-container>

Your EditModelingAgencyComponent Class:

import { Component, OnInit } from '@angular/core';
import { SharedService } from '../shared.service';

@Component({...})
export class EditModelingAgencyComponent implements OnInit {

  userIdToEdit;

  constructor(private sharedService: SharedService) { }

  ngOnInit() {
    this.userIdToEdit = this.sharedService.userToEdit;
    console.log(`Got the userId to edit as : ${this.sharedService.userToEdit}`);
  }

}

You can refer to this Sample StackBlitz for any ref.

Yes,You can use some service to save the selected item from the place you are clicking on the link before routing to editModelingAgency route and loading the same in the EditModelingAgencyComponent component on loading.

Another way is to set the selected id in some localstorage so that you can use the value in the EditModelingAgencyComponent.

You can simply add

 skipLocationChange: true

You can't pass data between components in url and hide the parameters, you have to use another way (using a service for example).

Please check this https://stackoverflow.com/a/48763597/10057411