I FUCKING DID IT

Added a helper component for managing a list of strings.
This component could, in theory, also be turned into a generic one
for any type of data

frontend-reactive/app/components/util/string-array.ts

@@ -0,0 +1,57 @@
+import MutableArray from '@ember/array/mutable'
+import { action } from '@ember/object'
+import Component from '@glimmer/component'
+import { tracked } from '@glimmer/tracking'
+
+export interface UtilStringArraySignature {
+  // The arguments accepted by the component
+  Args: {
+    list: MutableArray<{ value: string }>
+    prefix: string
+  }
+  // Any blocks yielded by the component
+  Blocks: {
+    default: []
+  }
+  // The element to which `...attributes` is applied in the component template
+  Element: null
+}
+
+export default class UtilStringArray extends Component<UtilStringArraySignature> {
+  @action addElement() {
+    MutableArray.apply(this.args.list)
+    this.args.list.pushObject({ value: '' })
+  }
+
+  @action removeElement(event: MouseEvent) {
+    MutableArray.apply(this.args.list)
+    const target = event.target as HTMLDivElement
+    const splits = target.id.split('-', 2)
+    if (splits.length != 2) return
+    const indexStr = splits[1]
+    //console.log('Content: ', indexStr)
+    if (!indexStr) return
+    //let index = this.args.list.find((elem) => elem == content)
+    //let index = this.listCopy.findIndex((d) => d == content)
+    this.args.list.removeAt(Number(indexStr))
+  }
+
+  transformArrayIntoUsable(arr: Array<string>): { [key: number]: string } {
+    const out: { [key: number]: string } = {}
+    const tmp = arr.map((elem: string, index: number) => {
+      out[index] = elem
+      return elem
+    })
+    return out
+  }
+
+  countElemsInObj(obj: any): number {
+    let count = 0
+
+    for (var prop in obj) {
+      if (obj.hasOwnProperty(prop)) ++count
+    }
+
+    return count
+  }
+}